When inventor Roger Sawyer created his 'Emdrive' concept in 2000, everyone laughed at his design.

Nasa claimed the quantum vacuum plasma thruster went against the laws of physics, as did many others in the scientific community.

But now the space agency has found out that the fuel-free space drive, once described as 'impossible', actually works - it is just not sure why.

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When inventor Roger Sawyer created his 'Emdrive' concept (pictured) in 2000, everyone laughed at his design.Nasa claimed the quantum vacuum plasma thruster went against the laws of physics, as did many others in the scientific community

The finding could bring human deep space travel a step closer as well as reducing the cost and size of satellites.

The engine, called EmDrive, is relatively simple.

It provides thrust to a spacecraft by bouncing microwaves around in a closed container.

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Solar energy provides the electricity to power the microwaves, which means that no propellant is needed.

The implications for this could be huge.

For instance, current satellites could be half the size they are today without the need to carry fuel.

Solar energy provides the electricity to power the microwaves, which means that no propellant is needed.The implications for this could be huge. For instance, current satellites could be half the size they are today without the need to carry fuel

Humans could also travel further into space, generating their own propulsion on the way.

When London-based Sawyer came up with concept, the only team that took him seriously was a group of Chinese scientists.

In 2009, the team allegedly produced 720 millinewton (or 72g) of thrust, enough to build a satellite thruster. But still, nobody believed they had achieved this.

Now Pennsylvania-based scientist Guido Fetta and his team at Nasa Eagleworks have published a paper that demonstrates that a similar engine works on the same principles.

Their model, dubbed Cannae Drive, produces much less thrust at 30 to 50 micronewtons - less than a thousandth of the output of some relatively low-powered ion thrusters used today.

Nasa is yet to explain why its engine works. This could mean that either the results are wrong, or the space agency has confirmed a breakthrough in space propulsion.

MAN-MADE LEAVES COULD HELP HUMANS COLONISE SPACE

A functioning man-made leaf that absorbs water and carbon dioxide to produce oxygen, just like natural leaves, has been created by an art graduate.

The new material could provide a steady source of oxygen for humans on long missions in space and even help us colonise new planets.

Julian Melchiorri claims that the leaves could also transform life on Earth as we know it, because buildings could be clad with the material to oxygenate homes and polluted urban areas.

The Royal College of Art graduate told Dezeen that Nasa is researching ways to ensure a supply of oxygen over long journeys so that people can live in space, but that plants don't grow in zero gravity.

This material could allow us to explore space much further than we can now,' he said. Mr Melchiorri claims that he has made the 'first photosynthetic material that is living and breathing as a leaf does.'

Mr Melchiorri says that his material consumes very little energy and as a result he thinks it could be incorporated into modern buildings, to absorb carbon dioxide.

It could be used to clad facades, ventilation systems, he said. 'You can absorb air from outside, pass it through these biological filters and then bring oxygenated air inside.'